Comment on "Serotypes and susceptibility of Streptococcus pneumoniae strains isolated from children in Mexico".

Dear Editor: Villaseñor-Sierra and colleagues present data on the serotypes and antibiotic susceptibility of S. pneumoniae strains from 48 children 1 to 12 years of age with invasive infections and 50 carriers in Mexico from March 2000 to May 2005.1 Serotype distribution, in addition to incidence of disease, is an important parameter to assess conjugate vaccination and this information adds to the published data on pneumococcal serotype distribution in Mexico.2-16 Coverage of the currently licensed heptavalent conjugate vaccine (containing serotypes 4, 6B, 9V, 14, 18C, 19F and 23F conjugated to the carrier protein CRM197) and the investigational 10-valent vaccine (containing serotypes 1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F and 23F conjugated to protein D, diphtheria and tetanus carrier proteins) for meningeal, non-meningeal invasive infections and nasopharyngeal carriage are shown in table I of the article by Villaseñor-Sierra and colleagues.1 We would like to point out that there is currently another investigational vaccine, containing 13 serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F conjugated to the carrier protein CRM197) that would further expand coverage of pneumococcal serotypes causing disease in Mexico.17-18 Although it is not possible to calculate the exact coverage offered by the investigational 13-valent vaccine with the data presented, it would cover at least 78% of the meningeal isolates recovered in this study, compared to 58% and 65% of the heptavalent conjugate vaccine and investigational 10-valent vaccine, respectively. This expanded coverage of the investigational 13-valent vaccine is mainly due to inclusion of serotype 3, which is the second most common serotype isolated from patients with meningitis representing 13% of these isolates.1 Serotypes 6A and 19A, in addition to the most likely antibioticresistant serotypes (6B, 14, 19F and 23F) found in the heptavalent conjugate pneumococcal vaccine, are included in the investigational 13-valent vaccine, thus potentially offering expanded coverage for antibiotic-resistant disease shown to be prevalent in Mexico. The WHO has recommended the incorporation of the currently licensed heptavalent pneumococal conjugate vaccine into national immunization programs as a priority, globally.19 Many countries, including Mexico, have taken this action. The data from Villaseñor-Sierra and coworkers will help guide the incorporation of new generations of conjugate vaccines, with expanded serotype coverage into these programs.